Method and apparatus to make a semiconductor chip susceptible to radiation failure

Abstract

Methods and apparatus are provided for reducing the overall radiation hardness of a semiconductor chip. A radiation detector and a failure memory are provided. A disable signal or signals is produced by the failure memory. The disable signal is a required input to a user logic function, such as an off chip driver, an off chip receiver, a clock, or a static random access memory. When the radiation detector detects radiation, that detection is stored in the failure memory. The disable signal, when active, causes some or all of the user function to be inoperative. This invention is particularly important when the semiconductor chip is produced in a silicon on insulator (SOI) Complementary Metal Oxide Semiconductor (CMOS) process, which is naturally radiation resistant.

Description

FIELD OF THE INVENTION[0001]The present invention relates to semiconductor chips. In particular, the present invention relates reducing radiation hardness on chipsDESCRIPTION OF THE RELATED ART[0002]Very Large Scale Integration (VLSI) employing bulk substrate Complementary Metal Oxide Semiconductor (CMOS) technology has been one of the major success stories in recent years. Virtually all of the recent high performance microprocessors, as well as the Application Specific Integrated Circuit (ASIC) chips have been implemented in CMOS on a bulk substrate.[0003]Bulk substrate technology provides a relatively inexpensive foundation upon which to create the N-channel Field Effect Transistors (NFETs) and the P-channel Field Effect Transistors (PFETs) needed to make modern logic circuits, such as NANDs, NORs, and memory elements, such as latches, registers, and Static Random Access Memories (SRAMs). CMOS implemented on a bulk substrate technology is called bulk CMOS. Source and drain areas o...

AI Technical Summary

Benefits of technology

[0033]The present invention is a method and apparatus that preserves the power and performance competitive advantages of SOI CMOS or similar radiation-hard semiconductor products, but which is less radiation-hard and therefore can be more easily and more broadly marketed.

Problems solved by technology

Several limitations of bulk CMOS are beginning to limit continued increases in frequencies.

A first limitation of bulk CMOS is the relatively large amount of capacitance in the reverse-biased junctions associated with NFET and PFET drains.

Thus the capacitance of the drains of the NFETs and PFETs limit the performance of the microprocessor or the ASIC.

In these circuits, the sources of most of the Field Effect Transistors (FETs) in the stacks of NFETs and PFETs also often are switched from one voltage level to another, further adding to capacitance that must be switched, and thus degrading performance.

Undesired capacitance not only degrades performance, but also causes more power to be dissipated.

Power is becoming a serious problem.

Even when large computers or other electronic products are plugged into the wall, heat buildup calls for elaborate and expensive cooling mechanisms.

A second limitation of bulk CMOS is that the bodies of all NFETs are coupled to ground (or another suitable lower voltage).

Creation of semiconductor chips involves relatively high fixed costs.

The products have to be designed, requiring expensive design tools and engineering labor.

In addition, the fabrication of the products requires extremely expensive semiconductor tools and factories.

These failures are often called soft errors.

The United States government restricts foreign sale or export of such products to some countries.

SOI CMOS microprocessors, Static Random Access Memories (SRAMs), Dynamic Random Access Memories (DRAMs), and ASIC products are resistant enough to radiation to fall into the radiation-hardened microelectronic circuit category, and are therefore subject to export restrictions and market limitations.

Semiconductor products produced on such processes also have their markets limited by the United States Government munitions restrictions.

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